Thats the first thing you do is check all the cables. And check for dust in cable connections.

remove -reinstall ram ,make sure you plugged the P4 plug back in if you removed power supply ,that the square 4 pin plug ,
what did you use to clean it

You should be much more careful when cleaning. Some of the components you shouldn't even touch with your hands, never mind a wet cloth.

Its possible something is either damaged physically from cleaning, something is fried from touch or liquids or that something is logically incorrect like plugs not being wired up correctly. It could be a cable, a port, a component, a device or even just a scrape on the motherboard.

Check if your power supply is plugged into all the devices, double check all of the connections and cables thoroughly. If it is something on your motherboard that cant be fixed, most likely the whole board will need replacing.

Check the power connectors and make sure there is no dust stuck the connection as well.

Reseat CPU and RAM.

Hope this helps!
Bill

I have the same problem. All LEDs and fans are running but no booting and the PC is more silent than usual.

I'm trying to get it to a tech guys today. Hopefully they can find out what the problem is. I hope its something as simple as RAM or a loose connection. I'm not equipped to buy a new GPU or mobo.

The POST should still run at least. The RAM is first used at the splash screen. If it is your RAM then your computer will freeze or restart from the splash screen.

You've already tried another HDD, another screen and another graphics card. Luckily you're running out of options so you should be getting close!

I doubt its a disfunctional piece of hardware, though its possible. Its probably just a loose connection somewhere. What did you use to clean it?

I doubt its a corrupt BIOS, this can be fixed by taking out the CMOS battery. It a little flat silver battery on the motherboard. Putting it back will reset your BIOS. There is a remote chance that might work. It would explain why it doesn't beep on startup.

Otherwise it must be your motherboard that needs replacing. Hopefully you can find another solution, but thats the last resort. If its obviously none of the other components, then thats the weak link. I hope you find an alternative though, good luck.

Other than the BIOS, it cant be a software problem. The screen starting up has nothing to do with the O/S. It has to be one of the problems mentioned in this message. I would suggest trying a BIOS reset, otherwise start looking into replacing your motherboard if possible.

If you want to make sure first you can use a similar class motherboard to test your components. Thats a lot of work though.

Let us know how you fare

Mine was apparently a loose connection. All fixed now